Facilities manager Frankie Yee said in a complaint that the students shouted at Shen and Mok with a loudspeaker, caused disturbances, ignored his orders, and verbally insulted the three of them. He said that Shen was knocked down during the melee.

Media reports showed Gerald Ho Jun-him, a 30-year-old final-year graduate student in the nursing school, berating its vice-president and dean of students with loud and harsh remarks and accusing them of currying favour with the Chinese Communist Party.

The dispute over the wall was resolved three days later after three students ended a 44-hour hunger strike, and the university agreed to continue to allow the student union to manage the wall.

But a disciplinary investigation against the four students was started in late January, and on Friday the university’s student discipline committee concluded that behaviour had amounted to “misconduct”.

Letters to the students from the committee said their actions had breached several rules, including “defamation of, or assault on, or battery against, any staff member”, “refusal to comply with orders”, “any conduct detrimental to the reputation and well being of the university” and “wilful damages to or defacement of any property of the university”

The university’s student discipline committee ruled that Ho would be kicked out of the institution and not be allowed to reapply for entry, while Lam Wing-hang, a third-year student of social work and former student union president, would be suspended for a year.

Also penalised were Owan Li, a student representative in PolyU’s governing council, who was given 120 hours of community service, and Hazel Cheng Yuet-ting, former external vice-president in the student union, who was given 60 hours of community service.

“I am so sad that the freedom of expression in the city has fallen to such a state. It could not survive even in the universities here,” said Ho, who called himself as a supporter of Hong Kong’s independence.

However, Ho – who is a member of pro-independence group Student Independence Union and was targeted by several leftist newspapers in the city immediately after the clash – said he did not believe the committee’s decision was influenced by his political convictions.

Ho had finished a chemistry degree at Chinese University before he came to Polytechnic University. He said he had never joined any student demonstrations, but he was annoyed when all his pro-independence slogans were torn down by the school and decided to step out.

Lam said: “We were doing the right thing and striving for freedom of speech and academic freedom for the university, and we should not be punished. The school made these decisions to suppress the students. They are shameless and do not deserve to be called educators.”

Lam said four of them would consider the option of filing judicial reviews to challenge the rulings. Discussions with the current student union cabinet were expected.

The current executive committee of the student union said in a statement that it strongly condemned the university for using its decision to try to silence the students from making politically sensitive comments. It also expressed doubt about the committee’s sentencing principles.

Local politicians also criticised the institution. A spokesman from the Democratic Party said the sanction was too harsh and that that university might be trying to deter student protests with disproportionate punishments.

A university spokeswoman said she could not discuss details of the rulings, citing privacy concerns but said the conclusions were reached after a very thorough investigation with all the available information submitted.

She said: “[the university] is committed to nurturing good citizen and hopes to ensure that our students behave in a proper way and it will not tolerate any unruly behaviour.”